Google/Bing has a lot of these, try searching? Or at least try to ask more specific question so we can give you proper answer, for example which migration method you plan to use?
This is the beginning page for the walk through of Exchange migrations. There are tons of resources on TechNet that can walk you through what kind of migration to perform and then help you plan, and go step by step through the process.
All the resources are accessible through the above linked page.
